Keto Whoopie Pies with Marshmallow Filling — Low-Carb Gluten-Free

OOH! Keto whoopie pies — yes, please. I’ll take two.

These marshmallow-filled sandwich cakes are sticky, gooey, and satisfyingly sweet, just like the originals. The filling has the light vanilla flavor and airy texture of marshmallow fluff without any graininess or unpleasant aftertaste, making these a perfect keto-friendly treat to curb a sweet craving.

These whoopie pies are:

• Low Carb
• Keto
• Gluten-Free
• Refined Sugar-Free

Low Carb Whoopie Pies — Come on, You Know You Want One

These feel indulgent enough to be cheating, but they’re much lower in carbs than traditional whoopie pies. Each serving is under four net carbs and is a generous portion. I won’t pretend I didn’t finish one and consider a second — but one is usually more than enough.

The cakes are delightfully sticky, just like real marshmallow fluff. Fair warning: making the filling can be a bit messy, but the result is worth it.

Best Sweeteners for These Whoopie Pies

Sweeteners for the cakes

Use your preferred 1:1 baking sweetener for the cakes. Powdered erythritol, xylitol, or monk fruit blends all work well. I personally use a powdered monk fruit/erythritol blend because it mixes smoothly in batters and leaves no aftertaste.

A note on stevia: many people, including myself, find stevia becomes bitter when combined with chocolate, so I don’t recommend it here.

Safety note: Xylitol is toxic to dogs and cats. Keep it away from pets.

Sweetener for the marshmallow fluff

The marshmallow fluff requires allulose. It behaves differently from erythritol or monk fruit blends — it becomes sticky when heated and then firms up, which is essential for this recipe. I tried other combinations, but none mimic the texture of real marshmallow fluff as reliably as allulose.

Tips to Get the Cakes Perfect

Almond- and coconut-flour baking behaves differently from wheat baking. A few tips will help the cakes rise and stay tender:

1. Sift all dry ingredients. Sifting removes lumps from flours and powdered sweeteners and adds a touch of air to the mixture, lightening the batter.
2. Beat the wet ingredients until light and fluffy, then add them to the dry ingredients all at once.
3. Mix just until combined. Overmixing creates a dense batter. The finished batter will be much thicker than boxed cake mixes — that’s normal.
4. I used a muffin-top pan to get perfectly round cakes, but a cookie sheet and an ice-cream scoop work fine if you don’t mind slightly less uniform shapes.
5. Pat the batter mounds with wet fingers or the back of a damp spoon so the tops are smooth.
6. The cakes are done when the center springs back or a toothpick comes out clean. Avoid overbaking to prevent dryness.

Tips for Making the (Almost) Carb-Free Marshmallow Fluff

Allulose requires a gentler approach than sugar. Cook it slowly to avoid browning and bitterness:

• Combine water and allulose in a high-sided saucepan and stir gently. If allulose crystalizes on the pan walls it can burn and cause bitterness.
• Use a wet pastry brush to wipe down the sides of the pan before heating. Cook over medium heat until the syrup reaches 260°F — this takes about 10 minutes. Do not cook on high.
• While the syrup cooks, whip the egg whites to soft peaks in a stand mixer. With the mixer running on medium, slowly stream the hot syrup into the whites (wear oven mitts — the syrup is very hot). Then whip on high until glossy and stiff, about 4–6 minutes. Let it cool briefly before piping.

This marshmallow fluff uses allulose and egg whites, keeping the carb count very low. Two heaping tablespoons contain negligible carbs.

Keto Whoopie Pie Assembly

Assembly is quick once the cakes are cool. Slice each cake in half like a hamburger bun — be gentle because they’re tender. Xanthan gum in the recipe helps bind the structure since there is no gluten to do the job; a small amount makes a big difference in gluten-free baking.

Pipe or spoon in the marshmallow fluff. Because the filling is very low in carbs, I like to be generous — two layers of fluff make every bite wonderfully gooey. For storage, don’t stack filled whoopie pies; the filling can ooze out. Store them single-layer to keep them neat.

Serving and Storage Suggestions

Store finished whoopie pies in the refrigerator. Allulose remains smooth and doesn’t recrystallize like erythritol or xylitol can, so the filling stays creamy in the cold. The texture is slightly firmer straight from the fridge, which can make it even closer to classic marshmallow fluff.

These taste best on the first day. If you plan to serve them over several days, store the cakes and the filling separately in the fridge and assemble as needed. Unfilled, sliced cakes can be frozen, and the marshmallow fluff keeps in the refrigerator for about three days.

Looking for more handheld cake-like treats?

Low Carb Cupcakes with Roasted Strawberries and Creamy Vanilla

Keto S’mores Cupcakes With Sugar-Free Marshmallow Fluff

Salted Caramel Keto Cupcakes (Gluten-Free & Low Carb)

Pretty Little English Madeleine Cakes (Low Carb & Gluten Free)

Keto Whoopie Pies With Marshmallow Filling

Yield: 10

Prep Time: 10 minutes

Cook Time: 25 minutes

Additional Time: 20 minutes

Total Time: 55 minutes

Ingredients

Chocolate Whoopie Pie Cakes

• 2 eggs
• 1/4 cup unsweetened almond milk
• 1/4 cup melted unsalted butter
• 1 ounce melted unsweetened baker’s chocolate
• 2/3 cup powdered erythritol-monkey fruit blend (or your preferred low-carb sweetener)
• 1 cup almond flour
• 1/2 cup coconut flour
• 1 Tbsp cocoa powder
• 1 tsp baking powder
• 1/3 tsp xanthan gum
• 1 tsp vanilla
• A pinch of salt

Marshmallow Fluff Filling

• 1 1/2 cups allulose
• 2/3 cup water
• 2 large egg whites
• 1 tsp vanilla
• A pinch of salt

Instructions

Chocolate Whoopie Pie Cakes

1. Preheat oven to 350°F.
2. Prepare a muffin-top pan with nonstick spray or grease 10 wells with butter or coconut oil.
3. Add eggs to a mixing bowl and beat on high for 2 minutes.
4. Melt the butter gently; it should be warm but not hot.
5. Chop and melt the baker’s chocolate in 30-second intervals until smooth.
6. Add vanilla, almond milk, melted butter, and melted chocolate to the beaten eggs and blend until combined.
7. Sift almond flour, coconut flour, baking powder, xanthan gum, salt, cocoa powder, and powdered sweetener into a large bowl.
8. Gently fold the wet mixture into the dry ingredients until just combined. Do not overmix.
9. Spoon 1/4 cup of batter into each muffin-top well and smooth the tops.
10. Bake at 350°F for 10–12 minutes or until a toothpick comes out clean.
11. Cool the whoopie pies in the pan for 20 minutes before removing.

Marshmallow Fluff Filling

1. Combine allulose and water in a high-sided saucepan; stir gently and use a wet pastry brush to remove crystals from the pan walls.
2. Whip the egg whites with a pinch of salt to soft peaks in a stand mixer.
3. Over medium heat, cook the allulose syrup to 260°F. If it browns prematurely, the heat is too high.
4. With the mixer running, slowly pour the hot syrup into the whipped egg whites (use oven mitts). Continue whipping on high until glossy and firm peaks form, 4–6 minutes. Add vanilla and mix to combine.

Whoopie Pie Assembly

1. Slice cooled cakes in half carefully.
2. Pipe or spoon about 1/4 cup of marshmallow fluff into the center of each cake.
3. Top each with the remaining half and store covered in a single layer in the refrigerator.

Nutrition Information:

Yield: 10
Serving Size: 1

Amount Per Serving:
Calories: 132
Total Fat: 8.8g
Saturated Fat: 1.7g
Cholesterol: 37mg
Sodium: 33mg
Carbohydrates: 8g
Net Carbohydrates: 3.4g
Fiber: 4g
Sugar: 0.5g
Protein: 6g

Nutritional information is approximate. Erythritol and other sugar alcohols are typically excluded from net-carb counts because they have minimal impact on blood sugar. Net carbs = total carbs minus fiber.